1. Field of the Invention
The present disclosure relates to a developer conveyance apparatus for use in an image forming apparatus, and to a process cartridge equipped with the developer conveyance apparatus.
In the context of the present specification, a developer conveyance apparatus is an apparatus for conveying developer for image formation. For example, the developer conveyance apparatus includes a process cartridge, a developer replenishment cartridge, and a developer conveyance portion in an electrophotographic image forming apparatus.
An image forming apparatus is an apparatus configured to form an image on a recording medium. The image forming apparatus includes an electrophotographic copying machine, an electrophotographic printer (such as a light emitting diode (LED) printer and a laser beam printer), and an electrophotographic facsimile apparatus, all of which are configured to form an image on a recording medium by using an electrophotographic image forming process.
A recording medium is a substance on which an image is formed. The recording medium includes a recording sheet and an overhead projector (OHP) sheet.
2. Description of the Related Art
Conventionally, there has been known a process cartridge system in which an electrophotographic photosensitive member in an image forming apparatus and a process unit acting thereon are integrated into a cartridge, which is detachably attachable to the image forming apparatus main body. The process cartridge system helps to achieve an improvement in terms of operability since it enables the user to perform maintenance on the apparatus.
The process cartridge is formed by a cleaning device (hereinafter referred to as a cleaning unit), and a development device (hereinafter referred to as a development unit). The cleaning unit includes an image bearing member as the electrophotographic photosensitive member, and a cleaning member configured to clean the surface of the image bearing member. The development unit includes a development roller configured to supply developer to the image bearing member, and a developer storage portion storing developer.
On the other hand, as an example of a process cartridge system, a developer replenishment system is known. In this system, a developer replenishment opening of a developer replenishment cartridge and a developer reception port of a process cartridge are connected to each other, and developer is replenished from the developer replenishment cartridge to the process cartridge.
In the developer replenishment system, when new developer replenished from the developer replenishment cartridge and old developer in the development unit are unevenly mixed with each other, image trouble is caused. In view of this, as discussed, for example, in Japanese Patent Application Laid-Open No. 2010-014890 (See FIG. 4 thereof), a developer replenishment type process cartridge adopts the following construction:
The development unit is divided into a development portion and a developer storage portion. The development portion and the developer storage portion are connected to each other by openings provided at both ends in the rotational axis direction of the image bearing member (hereinafter referred to as the “longitudinal direction”). The developer storage portion is provided with a developer conveyance member for conveying the developer and a developer stirring member for stirring the developer. The developer is circulated within the development unit by the developer conveyance member and the developer stirring member, whereby the new and old developers are uniformly mixed with each other.
However, during transportation of the process cartridge, the developer in the developer storage portion may be pressed so as to be coagulated. In particular, when, during its transportation, the process cartridge is caused to assume an attitude in which the longitudinal direction thereof oriented in the vertical direction, with the downstream side in the conveyance direction of the developer conveyance member being at the bottom, the coagulated developer is gathered on the downstream side in the conveyance direction of the developer conveyance member. When the process cartridge is used in this state, the coagulated developer is further pressed and hardened by the developer conveyance member, so that there is the possibility of the requisite torque for driving the developer conveyance member being increased.
As a countermeasure against this problem, Japanese Patent Application Laid-Open No. 11-160985 (See FIG. 1 thereof) discusses a construction in which a clutch is provided in a drive gear row of the developer stirring member and the developer conveyance member. In the case where the developer stirring member and the developer conveyance member are driven by the same drive source, when an excessive load is applied to the drive source, the rotation of the developer conveyance member is stopped by the clutch, and only the developer stirring member is allowed to rotate.
Further, as discussed in Japanese Patent Application Laid-Open No. 2009-116039 (See FIG. 1 thereof), a construction is available in which a torque limiter is connected to a drive gear of the developer stirring member and in which, when an excessive load is applied, the driving of the developer stirring member is interrupted, with rotation being only allowed for toner seal pulling.
However, as discussed in Japanese Patent Application Laid-Open No. 11-160985 and Japanese Patent Application Laid-Open No. 2009-116039, in the case where a clutch or the like is provided in the drive gear row of the developer stirring member and the developer conveyance member, there is a fear of the apparatus being increased in size due to the provision of the clutch.
It might be possible to arrange the clutch within the developer storage portion in order to avoid an increase in apparatus size. However, when the clutch is arranged within the developer storage portion, the portion of the developer around the clutch is not conveyed by the developer conveyance member, so that there is the possibility of some developer being allowed to stay around the clutch.